# std::experimental::erase_if (std::unordered_map)

From cppreference.com
< cpp‎ | experimental

Defined in header `<experimental/unordered_map>` |  |
template< class Key, class T, class Hash, class KeyEqual, class Alloc, class Pred > void erase_if( std::unordered_map<Key, T, Hash, KeyEqual, Alloc>& c, Pred pred ); |  | (library fundamentals TS v2)

Erases all elements that satisfy the predicate pred from the container. Equivalent to

    for (auto i = c.begin(), last = c.end(); i != last;)
    {
        if (pred(*i))
            i = c.erase(i);
        else
            ++i;
    }

### Parameters

c | - | container from which to erase
pred | - | predicate that determines which elements should be erased

### Complexity

Linear.

### Example

Run this code

    #include <experimental/unordered_map>
    #include <iostream>

    template<typename Os, typename Container>
    inline Os& operator<<(Os& os, Container const& cont)
    {
        os << '{';
        for (const auto& item : cont)
            os << '{' << item.first << ", " << item.second << '}';
        return os << '}';
    }

    int main()
    {
        std::unordered_map<int, char> data{{1, 'a'},{2, 'b'},{3, 'c'},{4, 'd'},
                                           {5, 'e'},{4, 'f'},{5, 'g'},{5, 'g'}};
        std::cout << "Original:\n" << data << '\n';
        std::experimental::erase_if(data, [](const auto& item)
        {
            return (item.first & 1) == 1;
        });
        std::cout << "Erase items with odd keys:\n" << data << '\n';
    }

Possible output:

    Original:
    {{5, e}{4, d}{3, c}{2, b}{1, a}}
    Erase items with odd keys:
    {{4, d}{2, b}}

### See also

removeremove_if | removes elements satisfying specific criteria (function template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/experimental/unordered_map/erase_if&oldid=98563"